I have a long history with using mechanical climbing tools and was taken aback by the ergonomics of the SJ3. I had used the SJ2.1 but didn’t like the amount of stress that it put on my thumb joint in order to use the wooden friction brake. The good design of the SJ3 gave me an overwhelming sense of ease and softness of use.

Some observations:

・The release lever is natural to hold and depress. The bottom of the lever contacts the steel plates at the pulley giving a reassuring feeling.

・Because the Working End terminates on the far side of the device, the pulling side of the system is next to the climber.

・The swivel ensures that the Standing End can feed directly into the pulley. Hitch systems offer a 360 degree release potential, the climber may pull at any point on the top part of the hitch with a variety of hand positions. Mechanicals direct the hand into a position and so the addition of a swivel ensures that stress on the wrist is kept to a minimum.

・The streamlined locking function on the side plate offers a variety of techniques that would ordinarily be accomplished with bulky knots.

・The thumb brake is very soft in its use. As you can see from the two drawings the hand position for the SJ2.1 and SJ3 is quite different when descending. The addition of the swivel means that the device is further away from the karabiner meaning that the inside edge of the release hand can place comfortably on the smooth and flat back plate.

Comparison chart

The SJ3 is a heavier, more intricate and expensive tool that accommodates a wider range of ergonomics, technique, rope size and has double the service life. In my mind there is no choice between the two.

Swivels help to configure many types of rigging. For Arborists they are seen mostly at the harness bridge.
Traditionally a swivel rotates at the centre and has an attachment either side of it. For a long time there has been a variety of swivel length and attachment design, some small, some large and some with built in rubber keepers. Last year DMM released a new series of swivels that allows 1, 2 and 3 way motion. The 2 and 3 way motion is achieved with the addition of a steel pin that allows the attachment point to swing side to side.

Attaching multiple systems at the bridge is complex to do well, everything needs to remain aligned.
If you use mechanicals, double crotch and traverse then it is advisable to try a 2 or 3 motion swivel. Consider the length of the system. Do you want the climbing device to be near (Spiderjack) or far (Unicender)? One-motion swivels can offer compactness of system length, the much longer three-motion Nexus should not be chosen for Spiderjack or the Hitch Climber M rig technique.

For some DdRT systems a swivel may add additional twists into the system because the rope holds twists naturally so the bottom part of a swivel may be considered. The Focus with replaceable shackle is a good option here. (see picture above) and the swivel head waits unobtrusively for additional systems to add to it.

A swivel will always wear through quicker than a ring because it cannot rotate, this is unavoidable though made affordable with the DMM replacement shackles. The shackles can be used by themselves as compact and strong connection points, installed into a knotted, stitched or spliced termination.

The Treemotion Globe 5000 bridge has been certified for use with DMM swivels only.